Most problem behaviors are intermittent or transitory. Most youth who exhibit problem behaviors do so only during a single year, a pattern that holds true for all of the problems examined in this Bulletin. The next most common pattern is 2 years, and the third is 3 years (see table 1). This
Bulletin focuses on persistent serious delinquency and persistent problem behavior occurring for 2 years or more.

Across all three study sites, the prevalence of persistent problem behavior was generally consistent (see figure 1). Twenty to thirty percent of males were serious delinquents; 14–17 percent were drug users; 7–22 percent had school problems; and 7–14 percent had mental health problems. In Rochester, where a greater number of males dropped out of school than in the other sites, 22 percent of males had school problems. The dropout rate for boys in Rochester was 18.5 percent, as compared with 3.1 percent in Denver and 6.2 percent in Pittsburgh. Combining the overall figures and ignoring the high dropout rate in Rochester, roughly 25 percent of males were serious delinquents, 15 percent were drug users, 7 percent had school problems, and 10 percent had mental health problems.

Females were studied in Denver and Rochester, but not in Pittsburgh. Among females, the overall figures indicated that 5 percent were serious delinquents, 11–12 percent were drug users, 10–21 percent had school problems, and 6–11 percent had mental health problems (see figure 2). A greater proportion of males than females were persistent serious delinquents. Gender differences are small, however, when comparing drug use, problems in school, and mental health problems at each site.